This invention relates to reaction injection molded articles and methods of forming such molded articles, and more particularly it is concerned with a reaction injection molded article formed with threads and a method of forming such molded article.
Heretofore, in the art of producing reaction injection molded articles (hereinafter molded articles), such as foamed urethane molded articles, methods stated as follows have been known for clamping associated parts to the molded articles:
1. Following making of holes in the molded article, tapping and threading of bolts are performed for securing parts. PA0 2. Self-tapping of the molded article is effected for securing parts. PA0 3. Holes are made through the molded article, and parts are secured in place by means of a backing strip and bolts. PA0 4. Following making of holes in the molded article and tapping, helicoils are fitted and bolts are threadably connected to secure parts in place.
Of the aforesaid four methods known in the art, the third method capable of providing a relatively high screw clamping critical torque or a maximum clamping torque capable of clamping the part without damaging the molded article and the threads formed therein is most popular and usually used.
However, this method suffers the disadvantage that when clamping is carried out the backing strip might be forced against the molded article to cause same to buckle and sufficiently high clamping strength could not be obtained. An added trouble is that this method cannot be used for producing containers that must be hermetically closed because of the need to make through holes therein when the molded article is produced.